The Girl from Jones Beach is a 1949 American comedy film directed by Peter Godfrey and written by I. A. L. Diamond. The film stars Ronald Reagan, Virginia Mayo, Eddie Bracken, Dona Drake, Henry Travers and Lois Wilson. The film was released by Warner Bros. on July 16, 1949.

Can we draw the following conclusion?
Ronald Regan was a well known actor by the time that he starred in The Girl from Jones Beach in 1949.
It's impossible to say